Pressure sensitive adhesive tapes used in medical applications are placed against the skin of a human body for a predetermined period of time. In general, the adhesive tape is required to repeatedly expand and contract in accordance with the user's movements while on the skin as described in JP-A 2002-233545. When the pressure sensitive adhesive tape has limited elasticity and poor skin conformability, then the tape cannot smoothly follow the expansion and the contraction of the skin, and therefore may irritate the skin.
In addition, pressure sensitive adhesive tapes used in medical applications should be moisture-permeable and air-permeable. Pressure sensitive adhesive tapes with poor moisture-permeability or air-permeability are placed against skin, the tape may trap moisture produced by skin, and increase discomfort on the skin from trapped perspiration. This trapped moisture may result in irritation, including a rash on the skin.
Coating pressure sensitive adhesives in a pattern on a substrate has been proposed in the art to address moisture and air permeability. U.S. Pat. Nos. 6,495,229 and 6,953,602 (JP-A 2003-509121) disclose an adhesive article that comprises a substrate and a pressure sensitive adhesive layer provided on the surface of the substrate in a pattern, wherein the pattern of the adhesive layer has an adhesive free area of less than about 25% and wherein the adhesive article has a water vapor transmission rate of greater than about 2000 g/m2/24 hour. JP-UM-A 4-110723, JP-A 10-328231 and JP-A 10-33741 disclose a pressure sensitive adhesive tape having a pressure sensitive adhesive layer in a striped or wavy pattern provided on at least one surface of an air-permeable or moisture-permeable substrate, in which air permeation is facilitated through the space between the strips.
U.S. Pat. Nos. 2,940,868; 4,163,822; 5,633,007; and 5,782,787 disclose a medical adhesive sheet comprising a pressure sensitive adhesive layer with a pattern formed by solvent coating. U.S. Pat. No. 5,641,506 discloses a medical patch material with a support coated with a pressure sensitive hot-melt adhesive coating, formed by means of gravure printing, that a) forms coherent webs in the lengthwise and transverse direction, which include island-shaped adhesive-free areas; b) has the proportion of the adhesive-free areas amount to between 30 and 60%, preferably between 40 and 57% of the total surface, and c) has a coat weight of the adhesive amount to between 30 and 160 g/m2, preferably between 40 and 120 g/m2.
However, patterned adhesives known in the art have the following problems. The patterned adhesives lack skin conformability at least in part because the patterned adhesives fail to conform to the pattern of skin and fail to remain elastic substantially irrespective of direction, like the skin. Rather, the tape may interfere with the expansion and the contraction of skin in one or more directions, causing mechanical irritation. Further, the patterned adhesives can either be difficult to coat finely divided patterns or fail to retain the pattern over time.